aurangzebhaque
Newbie level 5
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Hi,
I am a newbie and am trying to design an Amp-Hour meter using ATMega16. My main constraint is that I need to measure on the High side. The second constraint is that the high side current measurement ICs are not available locally in Karachi, Pakistan.
The current measurement is for a UPS battery (12VDC car battery). Current sensing is to be done with a shunt resistor giving 60mv/50Amps; being attached to the (+) line. Current flow is bi-directional i.e. load current and battery charging current.
The ATMega16 was purchased in DIP package and as such the gain stages are not available. Therefore I have to resort to using off the shelf op-amps. I have researched the Net and have come up with the initial design using work by Bonnie Baker of Microchip. The attached ZIPPED Excel sheet has been developed to model the IA based on LM324, Circuit used is also attached separately here.
I have the following questions about the IA configuration.
1. Will it be possible to power this IA from 12 Volt line in which the current is to be measured.
2. Can I connect the output of the IA directly to the ADC input of the ATmega without latchup issues and so forth. The ATmega would be running from a 7805, which (the 7805) would also derive its input voltage from the main 12 volt line.
3. Is it OK to keep VRef at 2.0 volts instead of Vcc/2. How do I generate this 2.0 Volts ?
Help in the matter is greatly appreciated.
Aurangzeb
I am a newbie and am trying to design an Amp-Hour meter using ATMega16. My main constraint is that I need to measure on the High side. The second constraint is that the high side current measurement ICs are not available locally in Karachi, Pakistan.
The current measurement is for a UPS battery (12VDC car battery). Current sensing is to be done with a shunt resistor giving 60mv/50Amps; being attached to the (+) line. Current flow is bi-directional i.e. load current and battery charging current.
The ATMega16 was purchased in DIP package and as such the gain stages are not available. Therefore I have to resort to using off the shelf op-amps. I have researched the Net and have come up with the initial design using work by Bonnie Baker of Microchip. The attached ZIPPED Excel sheet has been developed to model the IA based on LM324, Circuit used is also attached separately here.
I have the following questions about the IA configuration.
1. Will it be possible to power this IA from 12 Volt line in which the current is to be measured.
2. Can I connect the output of the IA directly to the ADC input of the ATmega without latchup issues and so forth. The ATmega would be running from a 7805, which (the 7805) would also derive its input voltage from the main 12 volt line.
3. Is it OK to keep VRef at 2.0 volts instead of Vcc/2. How do I generate this 2.0 Volts ?
Help in the matter is greatly appreciated.
Aurangzeb